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Coherent potential approximation
About: Coherent potential approximation is a research topic. Over the lifetime, 1930 publications have been published within this topic receiving 36805 citations.
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TL;DR: In this article, a quasiparticle method based on a multisite s(p) −d mixing model was used to calculate the exchange constants of dilute magnetic semiconductors.
Abstract: A quasiparticle method based on a multisite s(p)–d mixing model is used to calculate the exchange constants of dilute magnetic semiconductors (DMS). The effective interaction, which is mediated by s(p) electrons, between d electrons, was taken into account in an effective field approximation or a coherent potential approximation (CPA). The equation-of-motion technique was applied to Green functions to calculate the quasiparticle state density. The exchange constants were calculated in a double-valence-band model, and the microscopic parameter dependences of the exchange constants are investigated for fixed valence band parameters in the model. A ferromagnetic d–d coupling is obtained when the d energy level Ed is in the vicinity of the valence band top, and an antiferromagnetic d–d coupling is obtained when Ed is in the vicinity of the valence band bottom. The maximum of the d–d exchange constant Jd d(Ed) increases with the mixing strength. Jd d increases with decreasing Fermi energy EF, and the effect is more significant when Ed approaches the valence band top. Jd d also increases with small magnetic impurity concentration x, then reaches a maximum, and finally decreases sharply when x increases further. The quasiparticle state density shows that the ferromagnetism originates from the unsymmetrical broadening of the shallow d energy level in ferromagnetic alignment and related lowering of the centre of gravity of the d state density. Relevant experimental results are discussed on the basis of our calculation.
01 Jan 1994
TL;DR: In this article, a new method for calculating phase boundaries in alloys that uses the coherent potential approximation, the embedded cluster method, and the Monte Carlo method to predict phase boundary in binary alloy systems was described.
Abstract: We describe a new method for calculating phase boundaries in alloys that uses the coherent potential approximation, the embedded cluster method, and the Monte Carlo method to predict phase boundaries in binary alloy systems. The only input is the atomic number of the constituents, and the method is quite different in concept and execution from any other approach to this problem. Our phase boundary for the palladiumrhodium system is compared with others from the recent literature.
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TL;DR: In this article, a selfconsistent renormalization group approach analogous to the coherent potential approximation (CPA) in the band structure theory of disordered alloys has been developed.
Abstract: A self-consistent (SC) renormalization group approach analogous to the coherent potential approximation (CPA) in the band structure theory of disordered alloys has been developed. With the use of generalized CPA techniques a renormalization group equation in the local potential approximation (LPA) derived previously for spatially homogeneous systems has been extended to the lattice case and supplemented with a CPA-like self-consistency condition. To validate the approach it has been applied to the simple cubic Ising model and good agreement of the spontaneous magnetization calculated with the use of the SC-LPA equation with the available exact Monte Carlo simulations data has been established. Then the approach has been applied to the bcc Ising model corresponding to $\beta$-brass. With the use of the effective pair interaction values from available {\em ab initio} calculations the critical temperature, the correlation length and the long range order parameter in the vicinity of the critical point have been calculated in excellent agreement with experimental data. Quantitative arguments have been given in support of the suggestion that the experimentally observed large decrease of the effective critical exponent of the order parameter in comparison with its universal value is enhanced by the positive value of the second neighbour pair interaction found in the {\em ab initio} calculations.
01 Jan 1970
TL;DR: In this paper, the Hall conductivity and the orbital magnetic susceptibility in a weak magnetic field were calculated for binary alloys within the framework of coherent potential approximation, and two characteristic features coexisting, one inherent to propagating Bloch electrons and the other to localized atomic electrons, depending on the composition and the difference of atomic energy.
Abstract: The Hall conductivity and the orbital magnetic susceptibility in a weak magnetic field are calculated for binary alloys within the framework of coherent potential approximation. The model is the one of tight-binding limit with two kinds of atoms distributed at random over lattice sites. The atomic levels are assumed to be non-degenerate and the transfer energy is taken to be independent of the kind of atoms. The results show two characteristic features coexisting, one inherent to propagating Bloch electrons and the other to localized atomic electrons, depending on the composition and the difference of atomic energy.
TL;DR: In this paper, the electronic density of clusters composed from Ti and Cu was calculated in the local coherent potential approximation (LCPA) using real space representations and the muffin-tin approximation calculations were carried out for different composition rates and for different structures simulating the possible short range order of the amorphous alloys.
Abstract: The electronic density of states of clusters composed from Ti and Cu was calculated in the local coherent potential approximation (LCPA). Using real space representations and the muffin-tin approximation calculations were carried out for different composition rates and for different structures simulating the possible short range order of the amorphous alloys. By comparing the numerical results with experimental data one can collect arguments for the geometrical structure of these alloys.